This invention relates to fasteners such as nails, and the like, secured in strips for use in rapid-acting fastener driving tools.
Strips of nails and fasteners of similar types having elongated shanks joined together at the shanks by various expedients, such as wire, paper, and adhesives, or plastics, have come to be heavily used in connection with fastener driving tools to provide easy handling and loading and fast application to work. Such nail strips, and the driving tools in which they are used, have proved quite satisfactory in terms of speed and convenience.
However, with continuously increasing heavy usage, a growing need has arisen for more improvement in reliability, safety, ease of handling, etc., than is available by existing fastener strips. Existing disadvantages of the strips on the market include the breaking up of the carrier materials holding the fasteners together to produce particles upon the driving of a fastener which may stay inside the driving apparatus and increase the tendency of the apparatus to jam. Also, some carrier materials tend to shear away from the driven fastener at high velocities under the driving force of the fastener tool, with the result that particles are sprayed around, an obvious disadvantage from a safety standpoint.
Even when such barrier material has not been propelled from the tool, or has not become lodged inside to cause jamming, the separation of carrier material usually accompanying the use of prior art nail strips has given rise to equally undesirable accumulations of unsightly and often slippery debris about the work area. Also, carrier debris has tended to collect under the heads of nails and like fasteners, giving rise to both safety and finishing problems.
Essentially, a large number of carrier strips have been proposed, without complete success, to meet the following objectives, which are necessary in order to meet the strict demands of the relevant industries. These include the requirement that the strip be strong enough to be shipped, handled by the tool operators, and not destroyed inside the magazine while separation from the strip takes place. Each fastener and associated carrier material must be connected together and have a predetermined breaking point from the rest of the fasteners such that a single fastener with carrier material will be separated from the remaining strip and when driven will be carried along with the fastener and will leave no residue or carrier material on the working surface, exteriorly of the workpiece, or under the fastener head, after the fastener has been driven into soft and hard woods. The carrier must remain connected to the fastener during driving so that it does not clog the tool, thus causing malfunction of the tool, or be a potential source of injury to the tool operator, or a bystander by expelling debris from the tool. Furthermore, the strip must be economical to manufacture and be insensitive in performance to temperatures ranging from -10.degree.F. to 160.degree.F.
The prior art developments can be divided into two generalized catagories, hereinafter referred to as (a) single-component carriers and (b) two- or more-component carriers.
Single-component carriers are such as plastic materials extruded around fasteners, which plastic materials securely hold the fasteners in position. The strips are usually strong, rigid, economical to manufacture, and insensitive to elevated operating temperatures. However, at lower temperatures, these materials become extremely brittle, and the carrier breaks up when advanced inside the magazine. This results in carrier debris being expelled from the tool after the nail has been severed from the strip and the carrier breaks up into random pieces. Furthermore, with the frictional relationship between the fastener and carrier, the plastic breaks away from the nail during driving and does not enter the workpiece, which would prevent the debris scattering referred to above and the jamming of the tool resulting from loose pieces of carrier material in the driving chamber. Patents disclosing this type of nail strip is typified by U.S. Pat. Nos. 3,463,304 and 3,756,391. Some of the aforementioned deficiencies have been overcome by using wire as a carrier material, which is welded or staked to the nail. While such an approach overcomes the temperature problems and reduces the amount of debris, it increases the safety risk tremendously, because any small portion of wire breaking loose potentially leaves the tool like an uncontrolled projectile.
The typical two-component carrier material uses an adhesive of some sort to form an integral unit of fasteners and carrier with a general reduction in the amount of flying debris, which therefore minimizes jamming and increases the safety aspect. However, these adhesives have several disadvantages, including (1) they are by nature stickier, gummier and stick to the tools, which requires services work; (2) they do not have sufficient peel and/or shear strength to overcome the drive resistance of lumber; and (3) the acceptable adhesives fail to meet the total operating temperature range. By not having the desired peel and/or shear strength, the adhesive carrier will be shaved off the fastener when it enters the lumber and will be deposited under the fastener head and protrude therefrom, or remnants will be left on the workpiece. In the case of adhesives being used, since they are not able to operate during the total range of operating temperatures, it is necessary to utilize different adhesives under different temperature conditions, which has obvious disadvantages and causes double inventories and complicated and unreliable performance. Typical of this type of nail strip are those disclosed in U.S. Pat. Nos. 3,276,576, 3,515,271, and 3,625,352.